We have detected your current browser version is not the latest one. Xilinx.com uses the latest web technologies to bring you the best online experience possible. Please upgrade to a Xilinx.com supported browser:Chrome, Firefox, Internet Explorer 11, Safari. Thank you!

AR# 14865

5.1i Constraints Editor - Adding a period constraint causes "ERROR: XdmHelpers:664 - Period specification..."


General Description:

When I fit a CPLD design with a PERIOD constraint on a TNM group, the following error is reported:

"ERROR: XdmHelpers:664 - Period specification "TS_CLK" references the TNM group "CLK", which contains only pad elements. Only synchronous elements are permitted in a period specification. If this group was intended to reference the synchronous elements driven by the pad(s), you may need to change the TNM property to a TNM_NET property, so that it will be traced forward from the pad(s)."


To work around this issue, change the group constraint from a TNM to a TNM_NET.

This problem is fixed in the latest 5.1i Service Pack, available at:


The first service pack containing the fix is 5.1i Service Pack 1.

AR# 14865
Date 01/18/2010
Status Archive
Type General Article
Page Bookmarked